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[dragonfly.git] / secure / lib / libcrypto / man / DSA_generate_parameters.3
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129.\" ========================================================================
130.\"
131.IX Title "DSA_generate_parameters 3"
aac4ff6f 132.TH DSA_generate_parameters 3 "2008-09-06" "0.9.8h" "OpenSSL"
984263bc 133.SH "NAME"
74dab6c2 134DSA_generate_parameters \- generate DSA parameters
984263bc 135.SH "SYNOPSIS"
8b0cefbb 136.IX Header "SYNOPSIS"
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137.Vb 1
138\& #include <openssl/dsa.h>
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139.Ve
140.PP
141.Vb 3
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142\& DSA *DSA_generate_parameters(int bits, unsigned char *seed,
143\& int seed_len, int *counter_ret, unsigned long *h_ret,
144\& void (*callback)(int, int, void *), void *cb_arg);
145.Ve
146.SH "DESCRIPTION"
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147.IX Header "DESCRIPTION"
148\&\fIDSA_generate_parameters()\fR generates primes p and q and a generator g
149for use in the \s-1DSA\s0.
984263bc 150.PP
8b0cefbb 151\&\fBbits\fR is the length of the prime to be generated; the \s-1DSS\s0 allows a
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152maximum of 1024 bits.
153.PP
8b0cefbb 154If \fBseed\fR is \fB\s-1NULL\s0\fR or \fBseed_len\fR < 20, the primes will be
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155generated at random. Otherwise, the seed is used to generate
156them. If the given seed does not yield a prime q, a new random
157seed is chosen and placed at \fBseed\fR.
158.PP
8b0cefbb 159\&\fIDSA_generate_parameters()\fR places the iteration count in
984263bc 160*\fBcounter_ret\fR and a counter used for finding a generator in
8b0cefbb 161*\fBh_ret\fR, unless these are \fB\s-1NULL\s0\fR.
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162.PP
163A callback function may be used to provide feedback about the progress
8b0cefbb 164of the key generation. If \fBcallback\fR is not \fB\s-1NULL\s0\fR, it will be
984263bc 165called as follows:
8b0cefbb 166.IP "\(bu" 4
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167When a candidate for q is generated, \fBcallback(0, m++, cb_arg)\fR is called
168(m is 0 for the first candidate).
8b0cefbb 169.IP "\(bu" 4
984263bc 170When a candidate for q has passed a test by trial division,
8b0cefbb 171\&\fBcallback(1, \-1, cb_arg)\fR is called.
984263bc 172While a candidate for q is tested by Miller-Rabin primality tests,
8b0cefbb 173\&\fBcallback(1, i, cb_arg)\fR is called in the outer loop
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174(once for each witness that confirms that the candidate may be prime);
175i is the loop counter (starting at 0).
8b0cefbb 176.IP "\(bu" 4
984263bc 177When a prime q has been found, \fBcallback(2, 0, cb_arg)\fR and
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178\&\fBcallback(3, 0, cb_arg)\fR are called.
179.IP "\(bu" 4
984263bc 180Before a candidate for p (other than the first) is generated and tested,
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181\&\fBcallback(0, counter, cb_arg)\fR is called.
182.IP "\(bu" 4
984263bc 183When a candidate for p has passed the test by trial division,
8b0cefbb 184\&\fBcallback(1, \-1, cb_arg)\fR is called.
984263bc 185While it is tested by the Miller-Rabin primality test,
8b0cefbb 186\&\fBcallback(1, i, cb_arg)\fR is called in the outer loop
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187(once for each witness that confirms that the candidate may be prime).
188i is the loop counter (starting at 0).
8b0cefbb 189.IP "\(bu" 4
984263bc 190When p has been found, \fBcallback(2, 1, cb_arg)\fR is called.
8b0cefbb 191.IP "\(bu" 4
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192When the generator has been found, \fBcallback(3, 1, cb_arg)\fR is called.
193.SH "RETURN VALUE"
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194.IX Header "RETURN VALUE"
195\&\fIDSA_generate_parameters()\fR returns a pointer to the \s-1DSA\s0 structure, or
196\&\fB\s-1NULL\s0\fR if the parameter generation fails. The error codes can be
197obtained by \fIERR_get_error\fR\|(3).
984263bc 198.SH "BUGS"
8b0cefbb 199.IX Header "BUGS"
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200Seed lengths > 20 are not supported.
201.SH "SEE ALSO"
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202.IX Header "SEE ALSO"
203\&\fIdsa\fR\|(3), \fIERR_get_error\fR\|(3), \fIrand\fR\|(3),
204\&\fIDSA_free\fR\|(3)
984263bc 205.SH "HISTORY"
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206.IX Header "HISTORY"
207\&\fIDSA_generate_parameters()\fR appeared in SSLeay 0.8. The \fBcb_arg\fR
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208argument was added in SSLeay 0.9.0.
209In versions up to OpenSSL 0.9.4, \fBcallback(1, ...)\fR was called
210in the inner loop of the Miller-Rabin test whenever it reached the
211squaring step (the parameters to \fBcallback\fR did not reveal how many
212witnesses had been tested); since OpenSSL 0.9.5, \fBcallback(1, ...)\fR
213is called as in \fIBN_is_prime\fR\|(3), i.e. once for each witness.
aac4ff6f 214=cut